Kinetic mechanism of myofibril ATPase - PubMed (original) (raw)

Kinetic mechanism of myofibril ATPase

Y Z Ma et al. Biophys J. 1994 May.

Abstract

The kinetic mechanism of myofibril ATPase was investigated using psoas and mixed back muscle over a range of ionic strengths. Myofibrils were labeled with pyrene iodoacetamide to measure the rate constants for the binding of ATP and formation of the weakly attached state. The velocity of shortening was measured by stopping the contraction at various times by mixing with pH 4.5 buffer. The transient and steady-state rates of ATP hydrolysis were measured by the quench flow method. The results fitted the kinetic scheme [formula: see text] The rate constants (or equilibrium constants for steps 1 and 6) were obtained for the six steps. k5 was calculated from the KM for shortening velocity, K1, and k2. The rate constants were essentially equal for myofibrils and acto-S-1 at low ionic strength. Increasing the ionic strength up to 100 mM in NaCl increased the rate of the hydrolysis step and the size of the phosphate burst and the effective rate of product release became the rate-limiting step. The step calculated from the velocity of shortening, k5, and k2 is 15 nm, based on a model in which step 4 is the force-generating step.

PubMed Disclaimer

Cited by

Is SH1-SH2-cross-linked myosin subfragment 1 a structural analog of the weakly-bound state of myosin?
Bobkov AA, Reisler E. Bobkov AA, et al. Biophys J. 2000 Jul;79(1):460-7. doi: 10.1016/S0006-3495(00)76307-7. Biophys J. 2000. PMID: 10866971 Free PMC article.
Evidence for increased low force cross-bridge population in shortening skinned skeletal muscle fibers: implications for actomyosin kinetics.
Iwamoto H. Iwamoto H. Biophys J. 1995 Sep;69(3):1022-35. doi: 10.1016/S0006-3495(95)79977-5. Biophys J. 1995. PMID: 8519957 Free PMC article.
Unconventional myosins in inner-ear sensory epithelia.
Hasson T, Gillespie PG, Garcia JA, MacDonald RB, Zhao Y, Yee AG, Mooseker MS, Corey DP. Hasson T, et al. J Cell Biol. 1997 Jun 16;137(6):1287-307. doi: 10.1083/jcb.137.6.1287. J Cell Biol. 1997. PMID: 9182663 Free PMC article.
Mechanochemical coupling in muscle: attempts to measure simultaneously shortening and ATPase rates in myofibrils.
Lionne C, Travers F, Barman T. Lionne C, et al. Biophys J. 1996 Feb;70(2):887-95. doi: 10.1016/S0006-3495(96)79632-7. Biophys J. 1996. PMID: 8789106 Free PMC article.
Poorly understood aspects of striated muscle contraction.
Månsson A, Rassier D, Tsiavaliaris G. Månsson A, et al. Biomed Res Int. 2015;2015:245154. doi: 10.1155/2015/245154. Epub 2015 Apr 16. Biomed Res Int. 2015. PMID: 25961006 Free PMC article. Review.

References

1. J Biol Chem. 1991 Jan 5;266(1):294-302 - PubMed
1. J Biol Chem. 1990 Nov 25;265(33):20234-40 - PubMed
1. Nature. 1991 Jul 25;352(6333):301-6 - PubMed
1. Nature. 1991 Jul 25;352(6333):307-11 - PubMed
1. Nature. 1991 Jul 25;352(6333):352-4 - PubMed

Kinetic mechanism of myofibril ATPase - PubMed (original) (raw)